Cross-Sections and Components
Finishing the drafting
Last Class we got here:
The plan view of the cave looks great,
walls are in, geology symbols and the
details fill in the passage. It really is
starting to look like the cave you
surveyed
But we are missing information – not
from the plan view, or graphical, but
information about the cave that the
viewer needs
Cross-Sections and Components
Finishing the drafting
We are missing Cross sections
Yet, much of the value of a cave map lies in how
easily it can be understood by those who make use
of it. The task of cartographer is not just to
commit a cave to paper but also to make it easy
for the viewer to interpret and make use of. In this
light, the map user can immediately relate to a
cross-section, since it mirrors what they see while
inside the cave.
Cross-sections, being drawn from the perspective
of the caver, thus bridge this gap between
symbols on paper and reality, and provide a
recognizable reference for the end user. The
different parts of an in-cave sketch combine not
only to show what a cave does but what the cave is
like, and cross-sections are the weapon of choice
for describing the latter.
(Jeff Bartlett Arkansas Underground 4/2009)
Cross-Sections and Components
Finishing the drafting
We are missing Feature or Passage
names – to tell people where they are
in the cave
We are missing Passage information,
like ceiling height, depths of drops,
and distance above/below entrance
This is all valuable information for
someone moving through the cave
Cross-Sections and Components
Finishing the drafting
Cross Sections
Who doesn’t love cross sections?.
Cross sections should be used liberally to explain what the passage is doing. However it
can be a complex dilemma to get as much detail in without cluttering the map.
Likewise, complex cross sections can add a lot to the map if done well.
Cross sections should:
- either be scaled the same as the plan, or clearly called out as different
- Should have tic lines showing where they are being drawn in the cave
- Tic Lines should not contact map or cross section
- Should show direction sketcher is facing when drawing and up direction
- Detail in cross section should match plan
- Avoid gutless cross sections, don’t miss the complex areas!
- Adding bedrock symbols can help cross sections stand out
- Can be drawn Separate from plan – but must be located with labels
Cross-Sections and Components
Finishing the drafting
Remember, in cave and out, only draw what you know…
If you don’t know where the ceiling or the floor are, make sure you denote this on the
map
Water is too deep to
touch bottom
Unknown Ceiling
Cross-Sections and Components
Finishing the drafting
There are many different ways
to do cross sections
Cross-Sections and Components
Finishing the drafting
Unused Cross section
Moved Cross section
Cross Sections should be drawn right from the
in-cave sketch just like all other components of
the plan are.
This makes it important to do them correct in
the cave. They should be to the correct scale,
and have all the data needed in them.
Don’t be surprised if you draw more in-cave
then you place on your final map, or if you need
to move them to make the final map balanced.
Draw them first, and then move them
Cross-Sections and Components
Finishing the drafting
I usually add a layer for each part of the
cross section – walls, details and leader
lines
I usually draw all the cross sections in my
notes, and then move some to a hidden
layer if they are not used
Cross-Sections and Components
Finishing the drafting
One reason to keep the
cross-sections on a separate
layer, is you might decide to
flip the map. With the Cross
sections separate you will
just have to move them
instead of rotating each one
separately
In many cases you can even
reuse the leader lines
Cross-Sections and Components
Finishing the drafting
The Cross-sections are a lower hierarchy
(they should not stand out as much), so
they should be a lower line weight then the
walls
Here you can see that the walls are 2 point
lines, and the cross sections are 1 point
lines
Details can be .5 point.
Cross-Sections and Components
Finishing the drafting
Leader Lines (Tic Lines) have show several things, and have several parts
Leader Line
First, the leader line shows where in the cave the cross section is located. The line
should be drawn right through the exact location that the section represents
The line, however, Should NOT touch the walls of the cave
Cross-Sections and Components
Finishing the drafting
This tic represents the direction you are looking when the cross-section
was drawn. The cross-sections flip if they are drawn from the opposite
direction. Usually we draw them as if we are facing into the cave
This tic represents ‘up’. It is usually obvious, but as maps get copied
and rotated, sometimes this helps
Cross-Sections and Components
Finishing the drafting
Making Leader lines is easy:
Grab the Pen tool
Make the first tic, then draw straight
through the passage
Click to add a point, hit shift (to
draw a straight line) and draw right
through the cross section
Add your last tic
Cross-Sections and Components
Finishing the drafting
Now grab your scissors tool
Place it on the leader line, outside the wall
and click to cut
Do the same on the
opposite side
Highlight
And delete for a perfect leader
Do the same
for the Crosssection
Cross-Sections and Components
Finishing the drafting
Be Brave
Include several cross sections at a time, but take care to make sure that the
relative height in the cross-sections agree with how the cave really lines up in
real life. This data can be read from your compass data output
Cross-Sections and Components
Finishing the drafting
The same rules still apply about leader lines and tics, and
touching the walls – regardless of how many passages you
show in the cross -section
Cross-Sections and Components
Finishing the drafting
Lithology (symbols representing type of
rock) can be added. Above you see the
limestone surrounding the passage. Not only
does this make the passage really stand out,
but it shows exactly what happens – where
breakdown covers rock, or water, or sand…
However, modern cave survey techniques demand that the sketcher explain
whether, for example, a given wall is composed of solid limestone or whether it’s
an indeterminate jumble of breakdown blocks. Simple symbols are used to show
which portions of a passage outline are sediment or bedrock, and these “finish
the thought” for the map viewer as well as the cartographer working from your
sketches. (Jeff Bartlett – Arkansas Underground 4/2009)
Cross-Sections and Components
Finishing the drafting
I usually have the lithology as a symbol. I have various sizes based upon how large the cross
sections are . These were all hand drawn
Cross-Sections and Components
Finishing the drafting
Cross sections are drawn with a solid
line AND a solid fill. This allows them
to block the lithology behind them
Cross-Sections and Components
Finishing the drafting
Details are then drawn
on top of the crosssection on another layer
Layer control is
important here
Cross-Sections and Components
Finishing the drafting
The lithography can be shaped to
make it look less square with a large
white brush if desired
Cross-Sections and Components
Finishing the drafting
An even more detailed technique, where applicable,
is show specific stratigraphic layers. This is not particularly
common, and requires the sketcher to have
knowledge of geology and the ability to observe the
bedding planes; in some places, these are obvious to the
layman (a chert layer or nodules jutting out of a wall,
for example) while in others the difference between adjacent
limestone formations can be gradational or otherwise
indistinct.
However, in caves where the influence of multiple observable
strata have had a major impact on speleogenesis,
the extra effort may be well worth the trouble. The
USGS publishes a PDF list of suggested lithologic patterns
for common sedimentary rock on its website.
(Jeff Bartlett – Arkansas Underground 4/2009)
Cross-Sections and Components
Finishing the drafting
Many different patterns are available at
http://ngmdb.usgs.gov/fgdc_gds/geo
lsymstd/fgdc-geolsym-sec37.pdf
Cross-Sections and Components
Finishing the drafting
Other Data to be added: Ceiling height
Ceiling height is denoted by a number in a circle.
I usually write the number and then draw a
circle around it.
For the next one, I just copy and paste, and
then change the number. After a bit, you get a
lot of the common numbers
For the Ceiling heights it is OK to use a line
that touches the wall
Cross-Sections and Components
Finishing the drafting
However there are fonts available that will automatically provide
numbers inside circles
These are from http://cavediggers.com/fonts/
Cross-Sections and Components
Finishing the drafting
Sometimes the data can be placed inside
the passage.
This works well if you have enough room,
but I prefer to have mine outside
Cross-Sections and Components
Finishing the drafting
In deep water, we typically
use this adaptation of the
symbol – which means
height from water to
ceiling /depth of water
Coupled with a crosssection, it can describe
the passage excellently
Cross-Sections and Components
Finishing the drafting
There is no hard fast rule for how many
ceiling heights you should put in a map.
You want to inform people of major
changes, but not add so many that they
clutter up the map
Cross-Sections and Components
Finishing the drafting
Other Data to be added: Drops
Drops are signified by squares around numbers.
They should be coupled with a drop symbol.
We do this to indicate the drops, as well as to let
the caver know that ropes may be required
These can be hand drawn, or are
available as fonts as well
Cross-Sections and Components
Finishing the drafting
Other Data to be added: Datum (Vertical Control)
We usually designate the entrance as zero (O) datam
We can then give the height above or below the
datam in areas of the cave. These are marked
as the depth below /elevation above the
entrance with a bar over the number
This lets us know generally what the cave is
doing! In this example we can see the difference
in locations of these two close but vertically
separated passages
Cross-Sections and Components
Finishing the drafting
Other Data to be added: Names and Other Info
Add as much extra data as you can. People love to know where they are in a cave,
and be able to refer to it by name. These should have leaders and the leaders
should not touch the cave walls